I personally have never used anything but WinLESS, which is a wrapper for pure `less.js`, so that definitely works in praxis.
How about this:

If you download the original files, you need to compile Bootstrap's LESS files into usable CSS. To do that, Bootstrap only officially supports [Recess](http://twitter.github.io/recess/), Twitter's CSS hinter built on top of [less.js](http://lesscss.org).